Diseases associated with chronic hypoxemia like chronic obstructive pulmonary disease (COPD) or emphysema, represent major medical and socio-economical problems and one of the leading cause of morbidity and mortality in the western countries. Recently, is has been shown that cardiovascular (CV) diseases contribute highly to the morbidity and mortality of these patients. Furthermore, increasing evidence suggest that systemic vascular dysfunction play a central role in the mediation of the increased CV risk in patients with COPD. However the underlying mechanisms of vascular dysfunction in these patients are incompletely understood. Chronic mountain sickness (CMS) is characterized by chronic hypoxemia related at least in part to hypoventilation; it affects relatively young adults, and may therefore allow to study the effects of chronic hypoxemia. The investigators therefore will assess systemic vascular function and test the hypothesis that increased oxidative stress is responsible for this dysfunction. Since polyglobulia is a hallmark of chronic hypoxemia and has been suggested to affect vascular function, the investigators will test the effects of hemodilution on vascular function. Then, the investigators will test the effects of acute oxygen application and 1 month antioxidative dietary supplement on vascular function.

Preliminary data suggest that offspring of CMS patients may display pulmonary and systemic vascular dysfunction. Antioxidant administration is know to improve vascular function. We will test the acute effect of Vitamin C in this setting.

Finally, since there is considerable inter-individual variability of pulmonary artery pressure among CMS patients and the presence of a patent foramen ovale (PFO)is increased in clinical conditions associated with pulmonary hypertension and hypoxemia, we will assess the prevalence of PFO in healthy high altitude dwellers and in CMS patients and its effects on pulmonary artery pressure at rest and during mild exercise.

Inclusion Criteria:

• Patients with Chronic Mountain Sickness and their offspring

Exclusion Criteria:

• Smoking
• Lung disease
• Arterial Hypertension